Image scanners are widely used for scanning documents. For a purpose of successively scanning many paper sheets at a time, an automatic document feeder (ADF) is used for feeding the paper sheets into the image document one by one. By means of the automatic document feeder, the efficiency of scanning documents is enhanced.
Generally, an automatic document feeder is assembled by combining many mechanical elements including for example at least a roller, a shaft, a driving motor, a gear set and the like. In a case that the automatic document feeder has been used for a long term, some of these mechanical elements may be suffered from abrasion to some extent. For example, the surface material of the roller is readily abraded when the roller has rolled and contacted too many documents. Under this circumstance, since the friction resulted from the surface material of the roller is largely reduced or eliminated, the function of feeding the document becomes abnormal or two or more paper sheets are fed to the image scanner at a time. Therefore, the scanning operation is adversely affected. Similarly, the shaft hole is readily subject to abrasion when the shaft has been rotated and contacted the shaft hole for a long time.
A document feeder is described in Taiwanese Patent No. 593107, entitled “Sheet feeder with modular roller support and drive assembly, and the contents of which are hereby incorporated by reference. In the document feeder of Taiwanese Patent Gazette No. 593107, certain elements are formed as a replaceable module. If one or some elements contained in the replaceable module are damaged, the replaceable module can be detached from the automatic document feeder and replaced with a new one. The contents of this patent will be illustrated as follows in more details.
Referring to FIG. 1(a), a schematic view of a document feeder 10 described in Taiwanese Patent Gazette No. 593107 is illustrated. As shown in FIG. 1, the document feeder 10 principally comprises a document input tray 11, a driving motor 12 and a modular roller 20. The modular roller 20 is rotatably supported on the document input tray 11. The driving motor 12 is disposed at an end of the document input tray 11 for driving rotation of the modular roller 20. During operation of the automatic document feeder 10, the paper sheets are fed from upstream to downstream of the document input tray 11, i.e. in the direction indicated by the arrow A.
Referring to FIG. 1(b), a schematic view of the modular roller 20 is illustrated. The modular roller 20 principally comprises a shaft 21, a roller bogie 22 and a pair of spaced bogie support load arms 210, 212. By means of the bogie support load arms 210 and 212, the roller bogie 22 is mounted on the shaft 21. An axially gear 201 is driven by the driving motor 12 as shown in FIG. 1(a) so as to permit rotation of the whole modular roller 20. In addition, the modular roller 20 further comprises a swing arm 23 axially supported on the shaft 21. A clutch gear 231 is received within the swing arm 23 and synchronously rotated with the axially gear 201 so as to transmit a gear set 221 beside the roller bogie 22 to rotate. The modular roller 20 further comprises a stack stop 24 for feeding control of a stack of paper sheets placed on the document input tray 11.
The whole roller bogie 22 can be swung upwardly or downwardly by the related components of the swing arm 23 (not shown). For feeding the paper sheets with various thickness or height, a motion limit hook 232 is also integrally formed on the swing arm 23 for engagement with a paper separation roller axle 261, which is protruded from a paper separation roller (not shown) of the roller bogie 22, to restrain swinging height of roller bogie 22. The roller bogie 22 has a pre-feed roller 25 for engaging the top paper sheet to be removed from the stack of paper sheets. When the top paper sheet is transported with rotation of the pre-feed roller 25, the paper separation roller is also rotated to separate the top paper sheet from the stack of paper sheets so as to pick a single paper.
Referring to FIGS. 2(a), 2(b) and 2(c), schematic partial views of the roller bogie 22 mounted onto the shaft 21 are illustrated. As previously described, the roller bogie 22 is the major component of the modular roller 20 responsible for the paper picking operation. During the paper picking operation, the pre-feed roller 25 and the separation roller 26 of the roller bogie 22 should be rotated and the whole roller bogie 22 needs to be swung upwardly or downwardly. As a consequence, the roller bogie 22 should be pivotally mounted on the shaft 21.
As shown in FIG. 2(a), one end of the separation roller axle 261 of the separation roller 26 is movably received in a bearing aperture 291 of a support bearing 29. The support bearing 29 can be deflected to a certain extent such that the bearing aperture 291 is selectively opened or closed. As shown in FIG. 2(b), in a case that the bearing aperture 291 is opened, the separation roller 26 or the whole roller bogie 22 can be detached and then replaced with a new one. Whereas, in a case that support bearing 29 is deflected to have the bearing aperture 291 closed, as is shown in FIG. 2(c), the separation roller axle 261 of the separation roller 26 is enclosed and movably supported by the bearing aperture 291.
As previously described, the surfaces of the pre-feed roller 25 and the separation roller 26 of the roller bogie 22 are readily abraded when the document feeder 10 has been used for a long term. As a consequence, the function of performing the paper picking operation is impaired. Since the modular roller 20 is replaceable, the user can replace the modular roller 20 with a new one. The replacing task is convenient and can be serviced by the user without the necessity to involve a skilled service technician.
Although the modular roller 20 is easily replaced, there are still some drawbacks. For example, many components included in the modular roller 20 other than the pre-feed roller 25 or the separation roller 26 are not readily damaged components. Discarding these undamaged components along with the damaged pre-feed roller 25 or separation roller 26 is neither cost-effective nor environmentally-friendly. In contrast, if only the roller bogie 22 is replaced, the problem of impairing the paper picking operation remains because the bearing aperture 291 is still abraded upon rotation of the separation roller 26. Moreover, during the process of detaching the roller bogie 22, several complicated gears in the vicinity of the roller bogie 22 become hindrance from placing the roller bogie 22 in the right position.
In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop a document feeder according to the present invention through wholehearted experience and research.